Dynamoelectric machines such as small electric motors typically include a stator assembly having one or more windings, a rotor assembly rotatably mounted within the stator assembly, a shell or housing surrounding the stator assembly, and a motor endshield closing one end of the motor. The rotor assembly includes a rotating shaft which is supported in bearings. Such an electric motor is described in Keck et al., U.S. Pat. No. 3,482,128 which is assigned to the present assignee and incorporated by reference herein.
To connect the stator windings to an external power source, conductors usually are inserted through a notch formed in the motor shell. The conductors are connected at one end to the stator windings and the other end of the conductors are connected to the power source. The conductors are, of course, insulated by a plastic or rubber coating. As used herein, the term "motor leads" refers to such insulated conductors.
Although forming a notch in the motor shell is required for providing power to the stator from an external power source, the notch results in the undesirable consequence of potentially exposing the motor components to adverse external elements such as water, dirt and oil. Water, for example, could seep into the motor through the notch and damage the motor components.
In many electric motor applications, and in addition to protecting the motor components from exposure to water, dirt and oil, protecting the motor leads from such exposure also is desirable. Specifically, the portions of the leads extending within the motor housing and from the motor stator to the opening or notch formed in the motor shell are protected by the motor housing. The portions of the leads which are contained within the control unit or power source housing may be protected by such housing. The portions of the leads which extend between the motor shell and the control unit or power source housing, however, are exposed and usually require protection. If such portions of the leads are not protected, then the lead insulation may deteriorate and possibly expose the conductors. Such a condition is highly undesirable and could result in inoperability of the motor.
One form of motor lead protection is to increase the lead insulation thickness. Such thick insulation is more expensive than thinner lead insulation and results in increasing the cost of the motor. In addition, although such thick insulation may cover a portion of the notch formed in the motor shell, such thick insulation generally does not prevent water, dirt and oil from entering into the motor housing.
Other forms of protection include utilizing a hard molded plastic conduit, a semi-flexible metallic conduit, or a formed metal channel, sometimes referred to in the art and herein as "raceways", to protect the motor leads and partially cover the notch in the motor shell. One end of such a conduit or raceway may be inserted into the motor shell notch and the other end of the conduit or raceway may be brought into direct contact with the power source or control unit housing. The motor leads are disposed within the conduit or raceway.
With these forms of protection, one end of the conduit or raceway is inserted into the motor shell notch or is in close proximity to the notch. Such conduit or raceway end may be formed so as to cover a substantial portion of the notch. Substantially covering the notch provides some resistance against water, dirt or oil entering into the motor through the notch. However, water, dirt and oil may still rather easily pass through the notch and into the motor housing.
Manufacturing hard molded plastic conduits, metallic conduit and raceways also is expensive, and such conduits and raceways generally are not flexible enough for use in many applications. For example, since the length of the hard molded plastic conduit is fixed, in applications where the motor is disposed at a distance from the control unit which is greater than the conduit fixed length, a different conduit must be utilized to provide full lead length protection.
Terminal block assemblies for use with leadless motors also are utilized in coupling motor leads to external power sources or control units. An example of such an assembly is described in Keck, U.S. Pat. No. 4,851,725 which is assigned to the present assignee and incorporated by reference herein. With terminal block assemblies, a plurality of spaced apart motor leads and terminals are mounted in a terminal block housing. The terminal block housing receives a mating connector which is coupled to the external power source. Terminal block assemblies are useful in a variety of applications, however, such assemblies and the required mating conductors are expensive to manufacture. Also, although the terminal block assembly does protect the motor components from external conditions, the motor leads are exposed. To protect the leads in such an assembly, a separate sheath normally is utilized.
Commercially available couplings and conduits utilized to provide protection for wires also are known. For example, couplings available from Carlon, 25701 Science Park Drive, Cleveland, Ohio 44122, and sometimes referred to as Carflex.RTM. couplings, are utilized in applications such as protecting house wiring. Such couplings generally are molded from PVC and include a central member and completely threaded opposed bosses integrally formed therewith. An opening is formed through coupling to define a passage. One completely threaded boss is connected, for example, to an outdoor switching box and the other completely threaded boss is engaged to a conduit such as Carflex.RTM. conduit commercially available from Carlon or some other flexible conduit such as Liqua-tite.RTM. conduit available from Electri-flex Company, 222 West Central Avenue, Roselle, Ill. 60172. Since the fully threaded boss is connected to the conduit, the conduit typically must be fully rotated a number of times over the thread to provide full engagement. The connections are made utilizing, for the conduit, a sealing ring and a compression nut and, for the switching box, an o-ring and a lock nut. Wires from the switching box extend through the opening in the coupling and into the conduit.
The above-described assembly provides the advantage of utilizing an inexpensive flexible conduit to protect wires. In a high volume manufacturing process, however, requiring workers to fully rotate the conduit into full engagement with the completely threaded boss of the coupling is time consuming. Such rotation or twisting also is undesirable since requiring workers to perform such motion for an extended period of time could result in injuries such as carpel tunnel type injuries.
Accordingly, it is desirable and advantageous to provide an assembly for protecting motor components and leads extending between a motor shell and an external power source or control box housing which is inexpensive and easy to assemble. It is also desirable and advantageous to provide an assembly which is flexible so as to allow use of one assembly in many motor configurations for protecting such leads.
An object of the present invention is to provide an inexpensive and easy to manufacture and install assembly for substantially preventing water, dirt and oil from passing through the notch and into the motor and for protecting the leads for the entire lead length between the motor shell and control unit or power source housing.
Another object of the present invention is to provide a motor lead protection assembly which is flexible and can be used in many motor configurations.
Yet another object of the present invention is to provide a fitting for insertion into the notch formed in the motor shell and which is not easily separated from a flexible conduit having the motor leads extending therethrough.